The study reported in this paper was funded by the EPSRC (Fund code
EP/M507611/1) and Johnson Matthey PLC. The financial support by these
parties is highly appreciated.

The data required to reproduce each figure panel
is provided in different text files. Columns are separated by a space
character. The first line in each column describes the dataset.

With the added
context of the paper, it should be easy to reproduce the figures. The
data include original X-ray Diffraction, temperature and excitation
dependent photoluminescence measurements as well as the analysed data
presented in the figures of the paper.

Figure 1: XRD pattern of a sample grown at 150 °C. Inset: SEM image of the same sample.Figure 2: Temperature dependent PL of a sample shortly after growth. The excitation power for these measurements was set to 30 mW.

Figure 3:
(a) Temperature dependent PL of the zinc nitride sample after prolonged
exposure to ambient. (b) Comparison of the high-energy bands of the
same sample before (solid) and after (dashed) prolonged exposure to
ambient.

Figure 4: PL spectra of bands A and B at (a) 3.7
and (b) 294 K at different excitation powers. (c) Peak intensities and
(d) emission energies of band A at 294 K (●) and bands A (▼) and B (▲)
at 3.7 K as a function of excitation power. The spectra in (a) have been
normalised at the maximum intensity of band A.

Figure 5:
Temperature dependence of (a) relative integrated intensities (I/I0) and
(b) the emission energies of band A at an excitation power of 100 mW
(●) and bands A (▼) and B (▲) at an excitation power of 1 mW.